Method of and apparatus for the reception of radiosignals



July 21, 1925. 1,546,781

C. L. FARRAND METHOD OF AND APPARATUS FOR THE RECEPTION OF RADIOSIGNALSFiled Oct. 15, 1919 2 Sheets-Sheet 1 FIG.2.

INVENTOR 82 13 L. Farrand July 21, 1925. 1,546,781

c. L. FARRAND METHOD OF AND APPARATUS FOR THE RECEPTION OF RADIOSIGNALS2 Sheets-Shed 2 Filed Oct. 13, 1919 INVENTOR [air Z. Farrah BY MMATTORNEY I resistance variation differs slightly from the Ulhlllllt I).FARR/AND, @F SQUND BEACH, UUNNEUTEGUT, ASSIGN'O'R 0F ENE-THIRD lfi'attain CQRNELI'US D. lEHltET, @112 M O'UNJE AIMEE, PHIEADELFHIA,FENNSYLVAMA.

innrnon @E AND APPARATUS FOR THE RECEPTIIQN 01 aniolrosreirraris.

Application filed @ctober lml lt Serial 1%. teams.

To all whom it may concern:

Be it known that l, CLAIR L. FARRAND, a citizen of the United States,residing at Sound Beach, Fairfield County, State of Connecticut, haveinvented a Method of and Apparatus for the Reception of Radiosigrials,of which the following is aspecification.

The object of this invention is to provide methods of and means for thereception of radio telegraphic signals, particularly signals of undampedwaves.

My invention depends upon the discoveries, first, that the impedance ofa high he quency circuit can be varied at a high frequency rate; second,that the amplitude of the signal current varies at a frequencyequivalent to the difference between the frequency of the signal and thefrequency of impedance variation when the frequency of frequency of thesig'nal.

My invention, stated broadly, consists in the method of and apparatusfor the periodic regulation of amplitude of the high frequency signalcurrent, by means of a pcriodically changing impedance, whereby theregulationof amplitude corresponding in frequency to the difference infrequency between the frequency of the signal and the frequency .of theimpedance change is pro-- duced. p

The following is a description of .the method of and apparatus forattaining the above results, and will best be understood by referring tothe accompanying drawings,

,wherein the same numerals refer to corresponding parts in all figures.

Fig. 1 shows diagrammatically the method of practicing my lnventioninvolving a means of regulating the impedance of a secondary circuit ofa radio receiver; Fig. 2 shows diagrammaticallthe method of regulatingthe impedance 0 both primary and secondary circuits of a radio receiver;Fig. 3 shows diagrammatically the same method as Fig. 2, excepting thatthe impedance is varied for signal current when flowing in bothdirections; Fig. 4 shows diagrammatically the method involving themechanical means of varying the coupling co-efiicient between twocircuits of a high frequency inductor alternator inconjunction with adetector; Fig. 5 shows diagrammatically the method involving the samemechanical means as Fig. 4, utilizing the low frequency currentcomponent of the alternator to actuate the telethree-electrode vacuumvalve 11. The grid 13 is interposed-between plate 14: and filament 12,and a high frequency alternating potential is applied from source 17.With some types of valves it is advisable to include a negativepotential battery 16 for the grid circuit. It will be understood bythose skilled in the art that the resistance of the plate filamentcircuit of valve 11 is very igh when the grid 13 is negative and willconsequently increase the impedance of the receiver circuit 4-5 veryslightly; however, as the grid 13 becomes more positive due to thealternation of the potential applied from source 17 the resistance ofthe plate filament circuit decreases, causing a correspond ing decreasein the impedance of the receiver circuit and producing a correspondingreduction in the amplitude of the signal current flowing therein.Inasmuch as the 1mpedance change of the receiver circu t is effected at.high frequency rate differing slightly in frequency from the frequencyof the, signal, the signal current changes in amplitude periodically ata rate corresponding in frequency to the difference between thefrequencyof the signal and the frequency of the impedance change. Thlsperiodically changing current, rectlfied, produces a low frequencycurrent corresponding 1n frequency to the difference between thefrequency of the signal and the frequency of the resistance change,

Referring to Fig. 2, the numerals show arts corresponding to Fig. 1. 18is an inluctance coupled to the primary and secondary circuits of thereceiver and connected to the plate filament circuit of thethree-electrode valve 11. In this manner the effective impedance of theprimary and secondary circuits are changed, producing a signalcorresponding in frequency to the difference in frequency between thefrequency of the signal and the frequency of the impedance change.

Referring to Fig. 3, the numerals show parts corresponding to Figs. 1and 2; 19 is a three-electrode vacuum valve comprising 20 the filament,21 the grid, and 22 the plate, 23 the filament heating battery, and 24the negative grid battery. The plate 14 of valve 11 and the filament 20of valve 19 are connected to one terminal of inductance 18; the filament12 of valve 11 and the plate 22of valve 19 are connected to the otherterminal of inductance 18; the sources of alternating potential 17 and25 are connected to the grids of valve 11 and 19, respectively. Thesesources of alternating potential 17 and 25 are shown as alternatorsmounted on a common shaft, but may consist of any common form ofoscillation generator. By the means shown in Fig. 3, the impedance ofthe receiver circuit is regulated for signal currents flowing in bothdirections.

3 is somewhat higher than that of the arrangement shown in Fig. 2.,

Referring to Fig. 4, the numerals 26. repsuitable form of detector maybe used. Due

to the variation of coupling coeflicient between circuit 4526 andcircuit 29-30- 5;; at a rate corresponding to the frequency of rotationof the alternator a signal is produced. The current in the detectorcircuit corresponds in frequency to the difference between the frequencyof thesignal, and the frequency of rotation of the alternator. Thealternator is shown having eight poles for clearness of illustration. Itis assumed that a sufficient number of poles would be usedto'obtainsynchronism with the signal at reasonable speed. The inductor typealternator has advantages over the type shown at frequencies of 'theorder of fifty thousand cycles per second.- v

Referringxto'Fig. 5, the numerals represent parts corresponding to Fig.4. The rotor wmding. of the alternator is tuned by The receptionefiiclency of the arrangement shown in F ig.

means of inductance 32 and condenser 33 in series with telephone 9 tothe difference in frequency between the frequency of the signal and thefrequency of rotation of the alternator,

As the broad underlying principle herein disclosed is capable-0f variousapplications, such as frequency conversion at radio frequencies as Wellas at audible frequencies, it is not intended to limit the scope of theinvention disclosed and claimed to the figures and apparatus shown anddescribed, but to include therein the variousmodifications ofapparatusand methods capable of periodically regulating the amplitude of the highfrequency signal current, such as the periodic extraction of energy byresistance, the periodic change of capacitive reactance, the periodicchange of inductive reactance, the periodic change of mutual capacitiveor inductive reactance, or the periodic change of coupling coefficient.All of these may be classed generally under, and are intended to beunderstood as comprehended by, the phrase the periodic change ofimpedance, as. used in the method. claims hereto appended.

Impedance variation at frequency different from the signal frequencyand, more specifically, at audio frequency is claimed in my priorapplication Serial No. 296,960, filed lVfay 14, 1919. i

Having thus described my invention, I claim:

1. The method of receiving and translating into a signal radio frequencysignal-representing energy, which comprises receiving and detecting thesignal-representing energy in a circuit whose impedance is alwaysfinite, independently varying the impedance of said circuit by 'varyingan impedance between finite limits at a frequency above audibility, andtranslating the current as modified by said impedance variation into asignal.

2. The method of receiving and translating into a signal radio frequencysignal-representing energy, whichcomprises receiving and detecting thesignal-representing energy in a circuit whose impedance is alwaysfinite, independently varying the impedance of said circuit by varyingan impedance between finite limits at a high frequency differingfrom thefrequency of the signal-representing energy, and translating the currentas modified by said impedance variation into a signal.

3. The method of receiving and translating into a signal radio frequencysignal-representing energy, which comprises rectify- 1ng the radiofrequency signal-representing energy in a circuit whose impedance isalways finite, independently varying the impedance of said circuit byvarying an im- Ski weaver above audibility, and translating into asignal the rectified current as modified by said impedance variation.

4. The method of receiving and translating into a signal radio frequencysignal-representing energy, which comprises rectifying the radiofrequency signal-representing energy in a circuit whose impedance isalways finite, independently varying the impedance of said circuit byvarying an impedance between finite limits at a high frequency differingfrom the frequency of the signal-representing energy, and translatinginto a signal the rectified current as modified by saidimpedancevariation;

5. The method of receiving and translating into a signal radio frequencysignal-representing energy, which comprises impressing the receivedenergy upon the anode cathode circuit of a thermionic impedance,independently varying theimpedanceof said circuit by varying animpedance at a frequency above audibility, and translating into a signalthe current in said circuit as modified by said impedance variation.

6. The'method of receiving and translating into a' signal radiofrequency signal-representing energy, which comprises impressing thereceived energy upon the anodecathode circuit'of a thermionic impedance,independently varyingthe impedance of said circuit at a high frequencydiffering from the radio frequency of the signal-representing energy toimpart to the current in said circuit an amplitude variation whosefrequency is equal to the difl'erenc'e between said radio and highfrequencies, and translating into a signal said amplitude variation ofsaid current.

7. The method of receiving and translating into a signal radio frequencysignal-representing energy, which comprises impressing the same upon acircuit including a thermionic impedance, independently varying theimpedance of said circuit by varying a second thermionic impedance at aredetermined frequency, and translating nto a signal the current asmodified by said. impedance variation.

8. The method of receiving and translating into a signal radio frequencysignal-rcpresenting energy, which comprises impressing the same upon acircuit including a thermionic impedance, independently varying theimpedance of said circuit by varying a second thermionic impedance at afrequency above audibility, and translating into a signal the current asmodified b-y-said impedance variation.

9. The method of-receiving and translating into a signal radio frequencysignal-representing energy, which comprises impress? ing the same upon acircuit including a ther- 111101110 impedance, independently varying theimpedance of said circuit bv \varving a second thermionic impedance at ahigh frequency differing from theradio frequency of saidsignal-representing energy, and translating into a. signal the currentas modified by said impedance variation.

10. The method of receiving and translating into .a signal radiofrequency signalrepresenting energy, which comprises impressing the sameupon a detector, independently varying the operation of said detector bya thermionic impedance varying in magnitude periodically at a frequencyabove audibility and translating into a signal the current as modifiedby said impedance variation. K

11. The method of receiving and translating into a signal radiofrequency; signalrepresenting energy, which comprises impressing thesame upon a thermioni detector, independently varying theoperaEon ofsaid detector by a thermionic impedance varying in magnitudeperiodically at a frequency above audibility, and translating into asignal the current as modified by said impedance variation.

12. The method of receiving and translating into a signal radiofrequency signal-r epresenting energy, which comprises impressing thesame upon a detector, independently varying the operation of saiddetector by .a thermionic impedance varying in magnitude periodically ata'high frequency differing from the radio frequency ofsaidsigrial-representing energy, and translating into a signal thecurrent as modified by said impedance variation.

13. The method of receiving and translating into a signal radiofrequency signalrepresenting energy, which comprises impressing thereceived energy upon a circuit with which is operatively related athermionic device comprising an anode, cathode and control electrode,periodically varying the potential of said control electrodeindependently of the received energy at a frequency above audibility,and translating the resultant impedance variations into an audiblesignal.

14. The method of receiving and translating radio frequency energy,whichcomprises impressing the received energy upon a circuit withwhichis operatively related a thermionic device comprising an anode,

cathode and control electrode, periodically varying the potential ofsaid control electrode independently of the received energy at afrequency above audibility, and efiect ing current variation by theresultant impedance variations.

15. Receiving apparatus for translating radio frequency currentcomprising a rectifying detector, means for impressing the receivedenergy thereon, a translating instrument controlled by said detector,means for independently varying the impedance of the detector circuitcomprising an associated thermionic impedance, and means for varying themagnitude of said thermionic impedance at a predetermined frequency.

16. Receiving apparatus for translating radio frequencycurrentcomprising a rectifying detector, means for impressing thereceived energy thereon, a translating instrument controlled by saiddetector, means for independently varying the impedance of the detectorcircuit comprising an associated thermionic impedance, and means forvarying the magnitude of said thermionic impedance at a predeterminedfrequency above audibility.

17. Receiving apparatus for translating radio frequency currentcomprising a rectifying detector, means, for impressing the receivedenergy thereon, a translating instru- .ment controlled by said detector,means for independently varying the impedance of the detector circuitcomprising an associated thermionic impedance, and means for varying themagnitude of said thermionic impedance at a high frequency differingfrom the radio frequency of the received energy.

18. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, and means associated therewith foreffecting independent impedance variation comprising a thermionic devicehaving an anode, cathode and field-producing means, and means forvarying the field produced by said means at a predetermined requencyabove audibility.

19. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, and means associated therewith tectorcircuit, and means associated therefor effecting independent impedancevariation comprising a thermionic device having an anode, cathode andfield-producing means, and means for varying the field produced by saidmeans at a high frequency difl'ering" from the radio frequency of thereceived energy.

20. Receiving apparatus for translating radio frequency-currentcomprising a dewith for effecting independent impedance var atlon comprsing a thermionic device havung an anode, cathode and control electrode,and means for varying the potential of said control electrode at afrequency above audibility.

21. Receiving apparatus for translatingradio frequency currentcomprising a detector circuit, and means associated therewith forefi'ecting independent impedance variation comprising a thermionicdevice havin an anode, cathode and control electrode, an means forvarying the potential of said control electrodeat a high frequencydiffering from the radio frequency of the received Receiving apparatusfor translating with for effecting independent impedance variationcomprising a path including a pair of thermionic devices in parallelwith said path and each comp-rising an anode and a cathode, theanode-cathode paths of said thermionic devices being reversely relatedto said path, field-producing means for each of said thermionic devices,and. means for varying the fields produced by said means at apredetermined frequency.

23. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, and means associated therewith foreffecting independent impedance variation comprising a. path including apair of thermionic devices in parallel with said path and eachcomprising an anode and a cathode, the anode-cathode paths of saidthermionic devices being reversely related to said path, field-producingmeans for each of said thermionic devices, and means for varying thefield produced by said means at a predetermined frequency aboveaudibility.

24. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, and means associated'therewith foreffecting independent impedance variation comprising a path including apair of thermionic devices in parallel with said path and eachcomprising an anode and a cathode, the anode-cathode paths of saidthermionic devices being reversely related to said path, field-producingmeans for each of said thermionic devices, and means for varying thefields produced by said means at a high frequency differing from theradio frequency of the received energy.

25. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, a second circuit containing a thermionicimpedance, a path traversed by the received energy, means 'for couplingsaid path to said circuits, and means for varying the received energy,means for coupling said path to said circuits and said circults to eachother, and means for varying said thermionic impedance at apredetermined frequency. I

27. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, a second circuit containing a thermionicimpedance, a path traversed by the received energy, means for couplingsaid path to said circuits, and means for varying said thermionicimpedance at a predetermined frequency above audibility.

28. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, a second circuit containing a thermionicimpedance, a path traversed by the received energy, means for couplingsaid path to said circuits and said circuits to each other, and meansfor varying said thermionic impedance at a predetermined frequency aboveaudibility.

29. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, a second circuit containing a thermionicimpedance, a path traversed by the received energy, means for couplingsaid path to said circuits, and means for varying said thermionicimpedance at ahigh frequency differing from the radio frequency of thereceived energy.

30. Receiving apparatus for translating radio frequency currentcomprising a detector circuit, a second circuit containing a thermionicimpedance, a path traversed by the received energy, means for couplingsaid path to said circuits and said circuits to each other, and meansfor varying said thermionic impedance at a high frequency differing fromthe radio frequency of the received energy.

31. Receiving apparatus for translating radio frequency currentcomprising a circuit, a thermionic device operatively related to saidcircuit and comprising an anode, cathode and control electrode, meansfor pcriodically varying the potential of'said control electrode atsuper-audible frequency independently of the received energy, and meanscontrolled by the resultant current.

32. Receiving apparatus for translating radio frequency currentcomprising a circuit, a thermionic device operatively related to saidcircuit and comprising an anode, cathode and control electrode, meansfor periodically varying the potential of said control electrodeindependently of the received energy at a frequency above audibility,and means for translatingthe resultant current into an audible si a1.

CLAIR L. FARRAND.

